Systems for producing a single crystal silicon ingot using a vaporized dopant

ABSTRACT

An ingot puller apparatus for producing a doped single crystal silicon ingot includes a housing defining a chamber, a crucible disposed within the chamber, and a dopant injector extending into the housing. The dopant injector includes a delivery module attached to and extending through the housing into the chamber. The delivery module includes a dopant injection tube positioned within the chamber and a vaporization cup positioned within the dopant injection tube and the chamber. The second valve selectively channels the liquid dopant into the vaporization cup and the vaporization cup vaporizes the liquid dopant into a vaporized dopant.

FIELD

The field relates to systems and methods for producing a single crystalsilicon ingot using a vaporized dopant.

BACKGROUND

In high resistivity silicon wafer applications, the resistivity of thesingle crystal silicon ingot from which the wafers are sliced may becontrolled by addition of various dopants to the melt. The dopants maybe used to compensate for various impurities (e.g., boron orphosphorous) in the source of polycrystalline silicon used to form amelt from which the silicon ingot is withdrawn.

When one or more dopants are added to achieve a target resistivity inthe ingot, certain dopants and/or impurities may accumulate in the meltdue to differences in the segregation coefficients of the compounds. Forexample, boron has a segregation coefficient of about 0.8 which allowsboron to be readily taken up into the growing ingot. Phosphorous has asegregation coefficient of about 0.35 which causes phosphorous toaccumulate in the melt relative to boron which is taken up more readily.Accordingly, as the ingot grows and the melt is depleted, phosphorousaccumulates in the melt altering the resistivity of the growing ingot.This can cause the resistivity to decrease and fall out of customerspecifications and/or for a type-change to occur in the ingot.

A need exists for methods for counter-doping a silicon melt during ingotgrowth to increase the length of the ingot that remains within customerspecifications. A need also exists for doping methods that allow for useof dopant source materials that are readily available and/or relativelyinexpensive and that allow the melt to be doped with relative ease.Further, an ingot puller apparatus that allows a liquid-phase dopant tobe used as the source of dopant is needed.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the disclosure, which aredescribed and/or claimed below. This discussion is believed to behelpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

SUMMARY

In one aspect, an ingot puller apparatus for producing a doped singlecrystal silicon ingot includes a housing defining a chamber, a crucibledisposed within the chamber, and a dopant injector extending into thehousing. The dopant injector includes a delivery module attached to andextending through the housing into the chamber. The delivery moduleincludes a dopant injection tube positioned within the chamber and avaporization cup positioned within the dopant injection tube and thechamber. The second valve selectively channels the liquid dopant intothe vaporization cup and the vaporization cup vaporizes the liquiddopant into a vaporized dopant.

In another aspect, an ingot puller apparatus for producing a dopedsingle crystal silicon ingot includes a housing defining a chamber, acrucible disposed within the chamber, and a dopant injector extendinginto the housing. The dopant injector includes an injection moduleattached to an outer surface of the housing. The injection moduleincludes a first reservoir for containing a liquid dopant, a secondreservoir for containing the liquid dopant, a first valve forselectively channeling the liquid dopant from the first reservoir to thesecond reservoir, and a second valve for selectively channeling theliquid dopant from the second reservoir to the chamber. The dopantinjector also includes a delivery module attached to the injectionmodule and extending through the housing into the chamber. The secondvalve selectively channels the liquid dopant into the delivery moduleand the delivery module vaporizes the liquid dopant into a vaporizeddopant.

In yet another aspect, an ingot puller apparatus for producing a dopedsingle crystal silicon ingot includes a housing defining a chamber, acrucible disposed within the chamber, and a dopant injector extendinginto the housing. The dopant injector includes an injection moduleattached to an outer surface of the housing. The injection moduleincludes a first reservoir for containing a liquid dopant, a secondreservoir for containing the liquid dopant, a first valve forselectively channeling the liquid dopant from the first reservoir to thesecond reservoir, and a second valve for selectively channeling theliquid dopant from the second reservoir to the chamber. The dopantinjector also includes a delivery module attached to the injectionmodule and extending through the housing into the chamber. The deliverymodule includes a dopant injection tube positioned within the chamberand a vaporization cup positioned within the dopant injection tube andthe chamber. The second valve selectively channels the liquid dopantinto the vaporization cup and the vaporization cup vaporizes the liquiddopant into a vaporized dopant.

Various refinements exist of the features noted in relation to theabove-mentioned aspects of the present disclosure. Further features mayalso be incorporated in the above-mentioned aspects of the presentdisclosure as well. These refinements and additional features may existindividually or in any combination. For instance, various featuresdiscussed below in relation to any of the illustrated embodiments of thepresent disclosure may be incorporated into any of the above-describedaspects of the present disclosure, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-section side view of an embodiment of an ingotpuller apparatus having a dopant injector.

FIG. 2 is a perspective view of the dopant injector shown in FIG. 1 .

FIG. 3 is a cross-section perspective view of the dopant injector shownin FIG. 1 .

FIG. 4A is a cross-section perspective view of the dopant injector shownin FIG. 1 .

FIG. 4B is a detailed cross-section perspective view of the dopantchamber shown in FIG. 4A.

FIG. 5A is a cross-section perspective view of the dopant injector shownin FIG. 1 .

FIG. 5B is a detailed cross-section perspective view of the dopantchamber shown in FIG. 5A.

FIG. 6A is a cross-section perspective view of the dopant injector shownin FIG. 1 .

FIG. 6B is a detailed cross-section perspective view of the deliverymodule shown in FIG. 6A.

FIG. 7 is a cross-section perspective view of the vaporization cup shownin FIG. 3 .

FIG. 8 is a graph of ingot resistivity as a function of ingot length.

FIG. 9 is a schematic of an example method of producing a single crystalsilicon ingot.

FIG. 10 is a schematic of an example method of doping a single crystalsilicon ingot.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION

An example ingot puller apparatus 100 is generally shown in FIGS. 1-8 .The apparatus 100 of FIGS. 1-8 may be used to counter-dope or dope theingot with a vaporized boron dopant as in the method described herein ormay be used with other liquid-phase dopants that may be vaporized belowthe melting point of silicon (about 1414° C.) in either the native form,or a hydrated form, or in a compound that is non-contaminating to thecrystal growth process.

Referring now to FIG. 1 , the ingot puller apparatus 100 includes aningot puller outer housing 102 that defines an ingot puller innerchamber 104 within the housing 102. A crucible 106 is disposed withinthe ingot puller inner chamber 104. The crucible 106 contains thesilicon melt 108 from which a silicon ingot 110 is pulled. The ingot 110is shrouded by a heat shield 112.

The ingot puller apparatus 100 includes a dopant injector 114 forinjecting liquid dopant into the ingot puller apparatus as the ingot 110is pulled from the silicon melt 108. The dopant injector 114 enables thesilicon melt 108 to be counter-doped with a liquid dopant multiple timesas the ingot 110 is pulled from the melt, increasing the resistivity ofthe ingot, increasing the portion of the ingot that is within customerspecifications (e.g., high resistivity), and increasing the efficiencyof the ingot puller apparatus.

The dopant injector 114 includes an injection module 116, a deliverymodule 118, and a first flange 120. The injection module 116 and thedelivery module 118 are each attached to the first flange 120, and theflange attaches the injection module and the delivery module to thehousing 102. Specifically, the housing 102 defines a dopant injectoropening 122, and the first flange 120 is attached to the housing suchthat the flange covers the dopant injector opening.

The injection module 116 is attached to a first side 124 of the firstflange 120 such that the injection module is positioned outside thechamber 104. The delivery module 118 is attached to a second side 126 ofthe first flange 120 such that the delivery module is positioned withinthe chamber 104. The injection module 116 receives dopant and channelsthe dopant to the delivery module 118, and the delivery module receivesdopant from the injection module and injects the dopant into the chamber104 as described herein. In this embodiment, the injection module 116receives a liquid dopant, and the delivery module 118 vaporizes theliquid dopant within the chamber 104 as described herein.

As shown in FIG. 2 , the injection module 116 includes a second flange128, a doping chamber 130 attached to the second flange 128, anactuation mechanism 132 positioned on top of the doping chamber, coolingfluid conduits 134 and 136 for channeling cooling fluid to the dopantinjector 114, a bellows 138 attached to the first flange 120 and thesecond flange 128, and ports 140, 142, and 144 for channeling materialinto and out of the dopant injector. The doping chamber 130 is attachedto a first side 146 of the second flange 128, the bellows 138 isattached to a second side 148 of the second flange 128 and the firstside 124 of the first flange 120, and the ports 140, 142, and 144 areattached to and extend from the doping chamber. The bellows 138 enablesthe injection module 116 to be positioned within the ingot puller innerchamber 104 proximate the silicon melt 108. Specifically, the bellows138 enables the injection module 116 to be moved vertically relative tothe silicon melt 108.

The cooling fluid conduits 134 and 136 include a cooling fluid supply134 and a cooling fluid return 136. The cooling fluid conduits 134 and136 extend through the actuation mechanism 132 and into the dopingchamber 130. The actuation mechanism 132 includes air cylinders 150 foractuating valves within the dopant injector 114 as described herein. Theports 140, 142, and 144 include an inert gas port 140 for supplying aninert gas to the dopant injector 114, a pressure sensor port 142 formeasuring a pressure of the doping chamber 130, and a vacuum port 144for generating a vacuum within the doping chamber.

As shown in FIG. 3 , the injection module 116 also includes a dopantaddition tube 152, a first reservoir tube 154 defining a first reservoir156, a second reservoir tube 158 partially defining a second reservoir160, a first valve 162, a second valve 164, an actuator 166, anactuation shaft 168, and a cooling jacket 170. The dopant addition tube152, the first reservoir tube 154, the first reservoir 156, and thefirst valve 162 are all positioned within the doping chamber 130. Thesecond reservoir tube 158, the second reservoir 160, the actuation shaft168, and the cooling jacket 170 all extend from the doping chamber 130.The second reservoir tube 158 circumscribes the actuation shaft 168 todefine the second reservoir 160 therebetween, and the cooling jacket 170circumscribes the second reservoir tube 158.

The dopant addition tube 152 is coupled to the first reservoir 156, andthe first valve 162 is selectively actuated by the actuation shaft 168to maintain or release liquid dopant within the first reservoir. Thedopant addition tube 152 receives liquid dopant and channels the liquiddopant to the first reservoir 156. The first valve 162 is closed andmaintains the liquid dopant within the first reservoir 156. Uponactuation by the actuation shaft 168, the first valve 162 opens andchannels the liquid dopant into the second reservoir 160 as describedherein.

The first reservoir 156 is coupled to the second reservoir 160, and thefirst valve 162 is selectively actuated by the actuation shaft 168 torelease liquid dopant within the first reservoir to the secondreservoir. The second reservoir 160 receives liquid dopant and channelsthe liquid dopant to the delivery module 118. The second valve 164 isclosed and maintains the liquid dopant within the second reservoir 160.Upon actuation by the actuation shaft 168, the second valve 164 opensand channels the liquid dopant into the delivery module 118 as describedherein. The cooling jacket 170 receives a cooling fluid from the coolingfluid supply 134 and returns the cooling fluid to the cooling fluidreturn 136. The cooling fluid cools the injection module 116 to preventthe injection module from overheating.

The ingot puller inner chamber 104 is maintained at a first pressure,and the doping chamber 130 is maintained at a second pressure greaterthan the first pressure. Specifically, the first pressure of the ingotpuller inner chamber 104 is maintained at a vacuum, and the secondpressure of the doping chamber 130 is maintained at atmospheric pressuresuch that the liquid dopant is also maintained at atmospheric pressure.In alternative embodiments, the first pressure of the ingot puller innerchamber 104 is maintained at a pressure below atmospheric pressure, andthe second pressure of the doping chamber 130 is maintained at apressure above the first pressure. Accordingly, the liquid dopant ismaintained at the second pressure (atmospheric pressure) until theliquid dopant is injected into the ingot puller inner chamber 104 wherethe pressure of the liquid dopant is reduced to the first pressure (avacuum).

The actuator 166 is positioned within the doping chamber 130 and iscoupled to the air cylinders 150 and the actuation shaft 168. The aircylinders 150 actuate the actuator 166, and the actuator 166 actuatesthe first valve 162 and the actuation shaft 168. The actuation shaft 168actuates the second valve 164. More specifically, in the illustratedembodiment, the actuator 166 is a linear actuator that translates thefirst valve 162 and the shaft 168 linearly to translate open the firstvalve and to translate the second valve 164 linearly to open the secondvalve. In alternative embodiments, the actuation shaft 168 is coupled toboth the first valve 162 and the second valve 164 and actuates both thefirst valve and the second valve. In some embodiments, the actuationshaft 168 independently actuates the first valve 162 and the secondvalve 164. In alternative embodiments, the actuation shaft 168 actuatesthe first valve 162 and the second valve 164 simultaneously. Forexample, the actuation shaft 168 may actuate the first valve 162 and thesecond valve 164 simultaneously such that the first valve 162 is closedwhen the second valve 164 is open and the first valve 162 is open whenthe second valve 164 is closed in order to maintain the first pressurewithin the ingot puller inner chamber 104.

The delivery module 118 includes a feed tube 172 and a vaporization cup174 positioned within the feed tube. The feed tube 172 is positionedwithin the ingot puller inner chamber 104 and channels vaporized dopantto the silicon melt 108. Specifically, the vaporization cup 174 isheated by radiant heat from within the ingot puller inner chamber 104and receives the liquid dopant from the second reservoir 160. The ingotpuller apparatus 100 includes a heating system 176 that melts thesilicon melt 108 and radiates heat into the ingot puller inner chamber104. The liquid dopant is vaporized into a vaporized dopant within theingot puller inner chamber 104 where the liquid dopant is vaporized byflash evaporation by heating the liquid dopant with the vaporization cup174 and reducing the pressure of the liquid dopant from the secondpressure to the first pressure by injecting the liquid dopant into theingot puller inner chamber 104.

The feed tube 172 has a distal end 178 furthest from the ingot pullerouter housing 102 and a proximal end 180 nearest the ingot puller outerhousing. A feed tube axis A extends through the distal end 178 and theproximal end 180 of the feed tube 172. The feed tube 172 may be made ofquartz or other suitable materials.

The feed tube 172 is moveable within the ingot puller inner chamber 104along the feed tube axis A. The feed tube 172 may be lowered into theingot puller inner chamber 104 toward the silicon melt 108.Specifically, the feed tube 172 is attached to the cooling jacket 170,and the cooling jacket is attached to the doping chamber 130. Thebellows 138 enables the doping chamber 130, the cooling jacket 170, andthe feed tube 172 to move along the feed tube axis A toward and awayfrom the silicon melt 108. By moving the doping chamber 130, the coolingjacket 170, and the feed tube 172, the distal end 178 of the feed tube172 moves between a raised position in which the distal end positionedaway from the silicon melt 108 and a lowered position in which thedistal end is positioned proximate the surface of the silicon melt 108.The heat shield 112 may include a channel 182 formed therein to providea pathway for the feed tube 172 to approach the silicon melt 108.

In the lowered position of the feed tube 172, the vaporized dopanttravels down the feed tube where it is directed to the surface of thesilicon melt 108. The vaporized dopant passes through the distal end 178of the feed tube 172 to contact the silicon melt 108 to cause thesilicon melt to be doped and/or counter doped. As the doping chamber130, the cooling jacket 170, and the feed tube 172 are moved from theraised position to the lower position, the distance between thevaporization cup 174 and the silicon melt 108 and the heating system 176may be changed (e.g., by an operator).

The vaporization cup 174 includes a receiver 184 and a vaporization plug186 positioned within the receiver and divides the receiver into aliquid reception portion 188 and a vapor channel portion 190. Thereceiver 184 and the vaporization plug 186 define the liquid receptionportion 188, and the receiver 184 defines channels 192 that channelvaporized dopant from the liquid reception portion to the feed tube 172.The vaporization plug 186 has a first end 194 and a second end 196 anddefines vaporization channels 198 extending from the first end to thesecond end that channel vaporized dopant from the liquid receptionportion 188 to the vapor channel portion 190.

Excess heat from the heating system 176 heats the vaporization plug 186,and the second valve 164 channels the liquid dopant from the secondreservoir 160 into the liquid reception portion 188 and onto thevaporization plug. The vaporization plug 186 vaporizes the liquid dopantinto vaporized dopant by flash evaporation by heating the liquid dopantwith the vaporization plug 186 and reducing the pressure of the liquiddopant from the second pressure to the first pressure by injecting theliquid dopant into the liquid reception portion 188. The vaporizationchannels 198 channel the vaporized dopant into the channels 192 of thevapor channel portion 190 which channel the vaporized dopant into thefeed tube 172 and to the silicon melt 108. Additionally, a process gas(e.g., argon) may be circulated through the doping chamber 130 throughthe inert gas port 140 for channeling the vaporized dopant through thevaporization cup 174 and the feed tube 172.

The pressure sensor port 142 enables measurement of the pressure withinthe ingot puller inner chamber 104. The vacuum port 144 enablespump-down and leak testing. The cooling jacket 170 cools the injectionmodule 116 to prevent the injection module from overheating

Example methods of the present disclosure are shown in FIGS. 9 and 10 .The method may be carried out by use of the ingot puller apparatus 100that is configured to produce a boron-containing gas from liquid-phaseboric acid. While the method may be described with reference to theingot puller apparatus 100 shown in FIGS. 1-8 to exemplify the method,the method should not be limited to the ingot puller apparatus 100unless stated otherwise.

With reference to FIG. 8 , in accordance with embodiments of the methodfor preparing a silicon ingot, a silicon melt is prepared in thecrucible 106 disposed within the ingot puller inner chamber 104 of theingot puller apparatus 100. The crucible 106 may be supported by asusceptor (not shown). The ingot puller apparatus 100 may be configuredto rotate the crucible 106 and/or move the crucible 106 verticallywithin the ingot puller apparatus 100.

To prepare the silicon melt, polycrystalline silicon is added to thecrucible 106. The polycrystalline silicon is heated to above the meltingtemperature of silicon (about 1414° C.) to cause the polycrystallinesilicon to liquefy into the silicon melt 108. The heating system 176 isoperated to melt-down the polycrystalline silicon. For example, one ormore heaters 200 below or to the side of the crucible 106 are operatedto melt-down the silicon.

Before or after the melt 108 is produced, the melt may be doped with adopant, typically an n-type dopant, to compensate for p-type impurities(e.g., boron) in the melt. The n-type dopant may be added before growthof the ingot 110 commences. By compensating the melt, the resistivity ofthe resulting ingot 110 may be increased. For example, the seed end ofthe ingot (i.e., the portion of the ingot nearest the ingot crown) mayhave a resistivity of at least about 30 Ω-cm or, as in otherembodiments, at least about 35 Ω-cm, at least about 40 Ω-cm, at leastabout 45 Ω-cm, at least about 50 Ω-cm, at least about 55 Ω-cm, at leastabout 60 Ω-cm or from about 30 Ω-cm to about 60 ohm-cm. Suitable n-typedopants include phosphorous and arsenic.

Once the melt 108 is prepared, the single crystal silicon ingot 110 ispulled from the melt 108. A seed crystal 202 is secured to a seed chuck204. The seed chuck 204 and seed crystal 202 are lowered until the seedcrystal 202 contacts the surface of the silicon melt 108. Once the seedcrystal 202 begins to melt, a pulling mechanism slowly raises the seedcrystal 202 up to grow the monocrystalline ingot 110. A process gas(e.g., argon) is circulated through the ingot puller inner chamber 104of the ingot puller apparatus 100. The process gas creates an atmospherewithin the ingot puller inner chamber 104.

Embodiments of methods of the present disclosure include providing asource of liquid-phase boric acid (H₃BO₃). The boric acid may berelatively pure such as about 99% pure or more, 99.9% pure or more, or99.99% pure or more. In some embodiments, the boric acid may berelatively isotopically pure (i.e., boron-11).

A boron-containing gas is produced from the liquid-phase boric acid. Thegas that is produced is generally in the form of boric acid (H₃BO₃) orderivatives thereof (B_(x)O_(y)H_(z) ⁺ complexes) and not othercompounds (e.g., diborane (B₂H₆) or boron dihydride (BH₂)). However, itshould be understood that other boron compounds may be added to theboron-containing gas.

The liquid-phase boric acid may be heated to above its vaporizationtemperature (about 300° C.) to produce a boron-containing gas. Forexample, the liquid-phase boric acid may be heated by heat radiated fromthe silicon melt 108 in the ingot puller apparatus 100 or by the heatingsystem 176.

Once the boron-containing gas is produced, the boron-containing gascontacts the surface of the silicon melt 108 to allow boron to diffuseinto the melt. Once boron enters the melt, boron compensates forphosphorous which has concentrated in the melt due to the relatively lowsegregation coefficient of phosphorous, thereby increasing theresistivity of the remaining portion of the ingot 110 that forms in theingot puller apparatus 100.

FIG. 8 is a graph 206 of ingot resistivity as a function of ingotlength. As shown in FIG. 8 , the silicon melt 108 may be counter-dopedas described herein multiple times as the ingot 110 is pulled from thesilicon melt. Specifically, the resistivity of the ingot 110 maydecrease as the ingot is pulled from the silicon melt 108 because of theconcentration of phosphorous. The silicon melt 108 may be counter-dopedwith the dopant injector 114 as described herein multiple times as theingot 110 is pulled from the silicon melt 108 to increase theresistivity of the ingot during production such that a larger portion ofthe ingot is within customer specifications (e.g., high resistivity).More specifically, as shown in FIG. 8 , the silicon melt 108 iscounter-doped twice as the ingot 110 is pulled from the silicon melt108. Accordingly, the dopant injector 114 increases the efficiency ofthe ingot puller apparatus 100 by counter-doping the silicon melt 108multiple times during production of the ingot 110 and maintaining theresistivity of a larger portion of the ingot within customerspecifications (e.g., high resistivity).

FIG. 9 is a flow diagram of a method 300 for producing a single crystalsilicon ingot from a silicon melt held within a crucible positionedwithin an ingot puller apparatus. The method 300 includes adding 302polycrystalline silicon to the crucible, and the crucible is disposedwithin an ingot puller inner chamber. The method 300 also includesheating 304 the polycrystalline silicon to cause a silicon melt to formin the crucible. The method 300 further includes pulling 306 a singlecrystal silicon ingot from the silicon melt. The method 300 alsoincludes injecting 308 a liquid dopant into the ingot puller apparatus.The method 300 further includes vaporizing 310 the liquid dopant into avaporized dopant within the ingot puller apparatus. The method 300 alsoincludes contacting 312 the vaporized dopant with a surface of the meltto cause the vaporized dopant to enter the melt as a dopant whilepulling the single crystal silicon ingot from the melt.

FIG. 10 is a flow diagram of a method 400 for doping a single crystalsilicon ingot pulled from a silicon melt held within a cruciblepositioned within an ingot puller apparatus. The ingot puller apparatusincludes a housing, a dopant injector extending into the housing, and aheating system positioned with the housing. The dopant injector includesa dopant injection tube positioned within the housing and a vaporizationcup positioned within the dopant injection tube and the housing. Themethod 400 includes heating 402 the vaporization cup using the heatingsystem. The method 400 also includes maintaining 404 a pressure of aninterior of the housing at a first pressure. The method 400 furtherincludes injecting 406 liquid dopant into the dopant injection tube andthe vaporization cup. A pressure of the liquid dopant is maintained at asecond pressure greater than the first pressure prior to injection intothe dopant injection tube and the vaporization cup. The method 400 alsoincludes vaporizing 408 the liquid dopant into vaporized dopant withinthe housing. The liquid dopant is vaporized by flash evaporation byheating the liquid dopant with the vaporization cup and reducing thepressure of the liquid dopant from the second pressure to the firstpressure by injecting the liquid dopant into the housing. The method 400further includes channeling 410 the vaporized dopant into the housingusing the dopant injection tube.

Compared to conventional methods for producing a single crystal siliconingot from a silicon melt, the systems and methods of the presentdisclosure have several advantages. Specifically, a larger portion ofthe ingot may be within customer specifications (e.g., high resistivity)and/or a type-change in the ingot may be prevented. More specifically,the systems and methods of the present disclosure control the rate ofdoping such that compensating boron is incorporated into the ingot toneutralize the effect of segregation by phosphorous. Thus, the net freecharge carriers may be maintained between limits over the length of theingot. Depending on the target resistivity of the ingot, controlling therate of doping may prevent a type change of the ingot from n-type top-type or in other examples, from p-type to n-type. Liquid-phase boricacid has a relatively low vaporization temperature which allows a dopantgas to be produced with relative ease. Additionally, the vaporizationcup may be placed within ingot puller housing which allows the heat ofthe melt and the heating system to vaporize the dopant. The feed tube ismoveable within the ingot puller apparatus such that the distance fromthe melt may be controlled which allows the rate of dopant addition tothe melt to be controlled. Accordingly, the systems and methodsdescribed herein increases the efficiency of the ingot puller apparatusby counter-doping the silicon melt multiple times during production ofthe ingot and maintaining the resistivity of a larger portion of theingot within customer specifications (e.g., high resistivity).

As used herein, the terms “about,” “substantially,” “essentially” and“approximately” when used in conjunction with ranges of dimensions,concentrations, temperatures or other physical or chemical properties orcharacteristics is meant to cover variations that may exist in the upperand/or lower limits of the ranges of the properties or characteristics,including, for example, variations resulting from rounding, measurementmethodology or other statistical variation.

When introducing elements of the present disclosure or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising,”“including,” “containing” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. The use of terms indicating a particular orientation (e.g.,“top”, “bottom”, “side”, etc.) is for convenience of description anddoes not require any particular orientation of the item described.

As various changes could be made in the above constructions and methodswithout departing from the scope of the disclosure, it is intended thatall matter contained in the above description and shown in theaccompanying drawing[s] shall be interpreted as illustrative and not ina limiting sense.

What is claimed is:
 1. An ingot puller apparatus for producing a dopedsingle crystal silicon ingot, the ingot puller apparatus comprising: ahousing defining a chamber; a crucible disposed within the chamber; anda dopant injector extending into the housing, the dopant injectorcomprising: an injection module attached to an outer surface of thehousing, the injection module comprising: a first reservoir forcontaining a liquid dopant; a second reservoir for containing the liquiddopant; a first valve for selectively channeling the liquid dopant fromthe first reservoir to the second reservoir; and a second valve forselectively channeling the liquid dopant from the second reservoir tothe chamber; and a delivery module attached to the injection module andextending through the housing into the chamber, wherein the second valveselectively channels the liquid dopant into the delivery module and thedelivery module vaporizes the liquid dopant into a vaporized dopant. 2.The ingot puller apparatus as set forth in claim 1 further comprising ashaft coupled to the second valve, wherein the shaft actuates secondvalve.
 3. The ingot puller apparatus as set forth in claim 1, whereinthe first reservoir and the second reservoir are maintained at apressure above a pressure of the chamber.
 4. An ingot puller apparatusfor producing a doped single crystal silicon ingot, the ingot pullerapparatus comprising: a housing defining a chamber; a crucible disposedwithin the chamber; and a dopant injector extending into the housing,the dopant injector comprising: an injection module attached to an outersurface of the housing, the injection module comprising: a firstreservoir for containing a liquid dopant; a second reservoir forcontaining the liquid dopant; a first valve for selectively channelingthe liquid dopant from the first reservoir to the second reservoir; anda second valve for selectively channeling the liquid dopant from thesecond reservoir to the chamber; and a delivery module attached to theinjection module and extending through the housing into the chamber, thedelivery module comprising: a dopant injection tube positioned withinthe chamber; and a vaporization cup positioned within the dopantinjection tube and the chamber, wherein the second valve selectivelychannels the liquid dopant into the vaporization cup and thevaporization cup vaporizes the liquid dopant into a vaporized dopant. 5.The ingot puller apparatus as set forth in claim 4 wherein the dopantinjection tube includes a first end positioned proximate a surface of amelt to direct the vaporized dopant to the surface.
 6. The ingot pullerapparatus as set forth in claim 4 further comprising a shaft coupled tothe second valve, wherein the shaft actuates second valve.
 7. The ingotpuller apparatus as set forth in claim 4 wherein the vaporization cupcomprises: a receiver; and a vaporization plug positioned within thereceiver, wherein the liquid dopant is injected onto the vaporizationplug and the vaporization plug vaporizes the liquid dopant into thevaporized dopant.
 8. The ingot puller apparatus as set forth in claim 7wherein the vaporization plug divides the receiver into a liquidreception portion and a vapor channel portion.
 9. The ingot pullerapparatus as set forth in claim 8 wherein the receiver defines channelsthat channel the vaporized dopant from the liquid reception portion tothe dopant injection tube.
 10. The ingot puller apparatus as set forthin claim 9 wherein the vaporization plug includes a first end and asecond end and defines vapor channels extending from the first end tothe second end, wherein the liquid dopant is injected onto thevaporization plug and the vaporized dopant is channeled into thechannels through the vapor channels.
 11. The ingot puller apparatus asset forth in claim 4 wherein the dopant injector includes a bellows formoving the dopant injection tube proximate the crucible.
 12. The ingotpuller apparatus as set forth in claim 4 further comprising a heatingsystem for heating the vaporization cup using radiant heat from theheating system, wherein the radiant heat from the heating system isexcess heat from the heating system as the heating system meltspolycrystalline silicon in the crucible.